1. Field of the Invention
This invention relates to a magnetic recording playback such as a video tape recorder for recording and playing back information using rotary magnetic heads.
2. Background Art
Recently, so-called 8 mm video tape recorders have been standarized and put on the market. In a 8 mm video tape recorder of that sort, the rotational diameter of a rotary magnetic head (the diameter of a rotary drum) is set at 40 mm and an angle at which a magnetic tape is wound on the rotary drum is set at 221 degrees. Video signals are recorded in a portion corresponding to the 180-degree winding angle, whereas PCM (pulse code modulation) audio signals are recorded in a portion corresponding to the 36-degree winding angle. The portion corresponding to the remaining 5-degree winding angle is left as a surplus area. The portion corresponding to the 36-degree winding angle is further divided into a portion a for use in recording clock signals, a portion b for use in recording data such as the PCM audio signals, a margin c for after-recording, and a video overlap for use in continuously recording video signals of the immediately preceding field. Moreover, tracking pilot signals f.sub.1, f.sub.2, f.sub.3, f.sub.4 are sequentially recorded in the whole portion corresponding to the 221-degree winding angle on a track by track basis. These pilot signals f.sub.1, f.sub.2, f.sub.3, f.sub.4 are treated as signals at frequencies of f.sub.H /58, f.sub.H /50, f.sub.H /36, f.sub.H /40, where f.sub.H is the horizontal synchronizing signal. A tracking error signal is formed from stroke components derived from the tracks on the left and right of the pilot signals continuously recorded on each track. The number of revolutions of the rotary magnetic head is set at 1,800 rpm in the NTSC system and 1,500 rpm in the PAL system since it is operated so as to record video signals. Furthermore, a plurality of portions (five portions) corresponding to the 36-degree winding angle are formed in the portion corresponding to the 180-degree winding angle so that only audio signals may be recorded therein.
The audio signal recorded in the 36-degree portion is so arranged as to have a sampling frequency of 2 f.sub.H (roughly 31.5 kHz), 10 quantizing bits, and 2 channels. However, the 10-bit data is converted (compressed) into an 8-bit data before being recorded on the magnetic tape.
On the other hand, the R-DAT (rotational head digital audio tape) system has recently been standardized in order to record and play back high-definition audio signals. The R-DAT has adopted a standard comprising a magnetic tape winding angle of 90 degrees, a rotary drum diameter of 30 mm, a sampling frequency of 48 kHz. 44.1 kHz or 32 kHz, 16 quantizing bits, and 2 channels.
The track corresponding to a 90-degree winding angle is, as shown in FIG. 4, divided into 16 portions and data shown in Table 1 is recorded in each portion. In this case, one block is composed of 288-bit data and the 8-bit data is converted (modulated) into 10-bit data before being recorded on the magnetic tape.
The frequency f.sub.ch represents a clock signal of 9.408 MHz.
As shown in Table 1, the data comprises (1) a subcode signal recording portion consisting of 2, 3, 4, (2) a tracking signal recording portion of 5, 6, 7, (3) a PCM audio signal recording portion of 8, 9, (4) a tracking signal recording portion of 10, 11, 12 and (5) a subcode recording portion of 13, 14, 15.
TABLE 1 ______________________________________ Number Frequency Angle of (micro- Signal (degree) blocks seconds) ______________________________________ 1 MARGIN 1/2 f.sub.ch 5.051 11 420.9 2 PLL 1/2 f.sub.ch 0.918 2 76.5 3 SUB-1 3.673 8 306.1 4 POST AMBLE 1/2 f.sub.ch 0.459 1 38.3 5 IBG 1/6 f.sub.ch 1.378 3 114.8 6 ATF 2.296 5 191.3 7 IBG 1/6 f.sub.ch 1.378 3 114.8 8 PLL (PCM) 1/2 f.sub.ch 0.918 2 76.5 9 PCM 58.776 128 4898.0 10 IBG 1/6 f.sub.ch 1.378 3 114.8 11 ATF 2.296 5 191.3 12 IBG 1/6 f.sub.ch 1.378 3 114.8 13 PLL (SUB) 1/2 f.sub.ch 0.918 2 76.5 14 SUB-2 3.673 8 306.1 15 POST AMBLE 1/2 f.sub.ch 0.459 1 38.3 16 MARGIN 1/2 f.sub.ch 5.051 11 420.9 TOTAL 90.000 196 7500.0 ______________________________________
There are two systems for recording and playing back digital audio signals on a magnetic tape using a rotary magnetic head. However, since the 8 mm video tape recorder is mainly designed to record video signals, its audio signal sampling frequency is low besides the sound quality is inferior to what is offered by the R-DAT. On the other hand, the R-DAT is disadvantageous in that it is incapable of recording and playing back video signals but can only play back audio signals.
There are two systems for recording and playing back digital audio signals on a magnetic tape using a rotary magnetic head. However, the sound quality is determined by the sampling frequency. The low sampling frequency device has failed to realize what is accomplished by the high sampling frequency device. Also, since the 8 mm video tape recorder is mainly designed to record video signals, its audio signal sampling frequency is low and besides the sound quality is inferior to what is offered by the R-DAT. In addition to the above disadvantage, the problem is that a 4-channel audio signal cannot be efficiently recorded and played back.